The math nobody shows you
The commission percentage on the label is never the real cost. To know what you lose, add up every layer on one sale: the platform's commission, the payment processor's transaction fee, the share of any monthly subscription divided across your sales, and payout or currency conversion costs. Rates differ between providers and change often, so do not trust a number from memory. Go read each service's current terms and total it up yourself.
Run the exercise on one typical sale. Take your price, strip each layer off one at a time, and look at what is left. Most creators discover at that moment that the total bite is far bigger than the percentage they had in their head, because they were only counting one layer instead of all of them.
This is not accounting for accountants. It is the single move that tells you whether you are working for yourself or for the platform. Do it once, properly, and you will never look at your sales the same way again.